Selective demethylation of trimethylpentanes to form triptane



June 24, 1947- v. HAENsEl. ETAL 2,422,672

`SELECTIVE DEMETHYLATION OF TRIMETHYLPENTANES TO FORM TRIPTANE 2Sheets-Sheet 1 Filed Sept. 30, 1943 A y"June 24, 1947. v. HAENsEL ETALSELECTIVE DEMETHYL-ATION OF TRIMETHYLPENTANES TO FORM TRIPTANE 2sheets-sheet "2 Filed Sept. 30, 1943 Patented June 24, 1947 T osFicl-z'SELECTIVE DEMETHYLATION F TRI- METHYLPENTANES T0 FORM TRIPTANE VladimirHunsel and Vladimir N. rpauen. mverside, Ill., assignors to UniversalOil Company, Chicago, Ill

Wan

Products a' corporation o! Dela- Application September 30, 1943, SerialNo. 504,456

3 Claims. (Cl. 26o-683.6) j

This invention relates to the conversion of hydrocarbons and moreparticularly to the conversion oian aliphatic hydrocarbon containing atleast six carbon atoms to the molecule into an aliphatic hydrocarbonhaving at least one carbon atom less tothe molecule.

We have shown that aliphatic hydrocarbons, and preferably paraiiinichydrocarbons having a 'branched chain structure, may be subjected toselective demethylation in the presence of hydrogen and a hydrogenatingcatalyst at a temperature of from about 350 to about 700 F. andpreferably of from about 400 to about 650'1". under a pressure ofsubstantially atmospheric to 1500 pounds per square inch, or more.Suitable catalysts comprise the metals of the iron group and theiroxides including iron, nickel and cobalt, and the noble metals, platinumand palladium, used as such or supported by carriers. Under someconditions of operation, selective demethylation may also be 'effectedin the vpresence of an oxide or sulde of chromium, molybdenum, tungstenand vanadium. A highly selective catalyst contains approximately 66 percent by weight of total nickel, 30 per cent of diatomaceous earth and 4per cent of oxygen, the latter being present with nickel as nickeloxide.

The present invention is characterized by one or more of thev followingfeatures, either singly or in combination.

(1) Selective demethylation of a branched chain aliphatic hydrocarbon inthe manner heretofore set forth, separating a fraction containingmethane from the products of said demethylation, subjecting said methanefraction to conversion into hydrogen, and supplying the resultanthydrogen to 4the demethylation process.

(2) Purifying the hydrogen being supplied to the demethylation processto remove any moisture which may 'be present therein'. The presence ofmoisture has been found to be detrimental to the catalyst employed inthe demethylation process and its substantial removal is essential foreiilcient operation of the demethylation process.

(3)` Close control of the temperature in the reaction zone of theselective demethylation process since experiments have shown that thetemperature employed is critical and, in accordance with the presentinvention, the control of` temperature is eii'ected by means of acirculating heat exchange medium.

(4) Maintaining a temperature differential between the inlet and outletof the demethylation reactor.

(5) Close fractionation of the charging stock to the process to separatea selected fraction for treatment in the selective demethylation processin order to obtain improved results therein.

(6) Close fractionation of the products from the demethylation process,`with recycle of particular fractions in order to obtain increasedyields of the desired product.

(7) Separation of a hydrogen-containing fraction and amethane-containing fraction from the demethylation products by ashingina plurality of zones maintained at successively decreased pressures.

The present invention is applicable to the treatment of aliphatichydrocarbons and particularly branched chain paraiiinic hydrocarbonscontaining at least six carbon atoms per molecule. It is also applicableto the treatment of naphthenic hydrocarbons containing alkyl sidechains, p

although the results obtained are not necessarily equivalent. Theinvention is particularly applicable to the production of triptane whichis otherwise known as 2,2,3-trimethy1butane.

In a. broad aspect the present invention relates to a. process forconverting an aliphatic hydrocarbon into an aliphatic hydrocarboncontaining at least one carbon atom less to the molecule, whichcomprises subjecting the nrst mentioned aliphatic hydrocarbon toselective demethylation in the presence of hydrogen and a hydrogenatingcatalyst under conditions to produce an aliphatic hydrocarbon having atleast one carbon atom less to the molecule, separating from thedemethylation products a methane-containing fraction, subjecting thelatter fraction to conversion to produce hydrogen'therefrom, andsupplying at least a portion of the resultant hydrogen to thedemethylation reaction.

In one specific embodiment the present invention relates Ito a processfor producing triptane which comprises heating a fraction containing2,2,3-trimethylpentane, simultaneously heating a hydrogen fractionsubstantially free of moisture, commingling the heated streams andintroducing the same at a temperature of from about 400 to about 650 F.into a reaction zone, maintaining the temperature in the reaction zonewithin a relatively narrow range by means of indirect contact with acirculating heat exchange medium, flashing the demethylation .productsto separate a hydrogen-containing fraction, further ashing the remainingproducts to separate a methanecontaining fraction, subjecting .themethaneing said hydrogen and commingling the same with said fractioncontaining 2,2,3-trimethylpentane as aforesaid.

The invention will be further explained in connection with the attacheddiagrammatic flow drawing comprising Figures 1 and lA which illustrateseveral specific embodiments of the invention. In the interest ofsimplicity, the description of the drawing will be limited to a processfor the treatment of an isooctane fraction for the production oftriptane. It is understood, however, that the broad scope of theinvention is not so limited, but that it is applicable, with suitablemodifications, to the treatment of other hydrocarbons. In general, thepreferred charging stocks are those containing at least ve carbon atomsto the molecule and having a quaternary carbon atom, and particularlythose having a triptyl group. By quaternary carbon atom it is meant acarbon atom which isA combined chemically with four other carbon atoms,neopentane being the simplest example of a hydrocarbon containing aquaternary carbon atom. By triptyl group it is meant a hydrocarboncontaining adjacent quaternary and tertiary carbon atoms; that is, onecarbon atom is combined chemically with four other carbon atoms and oneof said four carbon atoms is tertiary in that it is bound l to thequaternary carbon atom, to two other carbon atoms and to only onehydrogen atom.

The charging stock to the process of the present invention may suitablycomprise an isooctane fraction produced by the polymerization of normaland isobutylenes in the presence of suitable catalysts and particularlysulfuric acid, the latter polymerization being effected ata temperaturewithin the range of from about 150 to about 200 F., followed byhydrogenation of the polymerization products. The hydrogenated productsmay be subjected to fractionation or other treatment to separate anisooctane fraction having an initial boiling point of about 194 F. andcontaining 22,4-, 2,2,3-2,3,4, and 2,3,3-trimethylpentanes along withhigher boiling compounds.

The isooctane fraction charging stock, at a suitable temperature andpressure, is introduced to the process through line I containing valve 2and is directed into fractionator 3. Fractionator 3 may comprise anysuitable zone for effecting the separation of the products introducedthereto into the desired fractions and may suitably comprise afractionating column containing bubble trays, baille plates,side-to-side pans or other contact means. Fractionator 3 is preferablyheated at the bottom by means of closed coil 4 or other suitable meansand is cooled at the top in any suitable manner such as by recycling aportion of the condensed overhead fraction as will be hereinafterdescribed.

As applied to the particular isooctane fraction as heretofore set forth,zone 3 will be operated to separate an overhead fraction having aninitial boiling point of about'l94 F. and an end boiling point of about239 F. from higher boiling bottoms fraction. The higher boiling bottomsfraction is withdrawn from the lower portion of zone 3 through line 5containing valve 6 to storage or elsewhere as desired. The overheadfraction, which now comprises a mixture of the varioustrimethylpentanes, is Withdrawn from the upper portion of zone 3 throughline 1 containing valve 8 and is passed through condenser 9 and rundownline I containing valve Il into receiver I2, having conventional gasrelease line I3 containing valve I4. The condensate in receiver I2 iswithdrawn therefrom through line I5 containing valve I6 to pump I1, bymeans of which a regulatedportion thereof is recycled by way of line I8containing valve I9 to the upper portion ol fractionator 3 to serve as acooling and refluxing medium therein, while the remaining portion of thecondensate from yreceiver I2 is directed through line 20, valve 2 I,heat exchanger or other suitable heating means 2l to fractionator 22.

Fractionator 22 may be similar to heretofore described fractionator 3and contains closed coil 23 or other suitable heating means in the lowerportion thereof. This fractionator will function to separate an overheadfraction comprising hydrocarbons boiling below about 226 F from higherboiling trimethylpentanes. The light fraction withdrawn as an overheadproduct from fractionator 22 will comprise principally 2,2,4-trimethylpentane and 2,3-dimethylpentane, the latter being produced inthe process as will be hereinafter set forth. This fraction is directedthrough line 24 containing valve 25 into and through condenser 26,rundown line 21 and valve 28 into receiver 29, having conventional gasrelease line 30 containing valve 3l. The condensate in receiver 29 maybe withdrawn therefrom through line 32 and valve 33 to pump 34, by meansof which a iegulated portion thereof may be recycled by way of line 35and valve 36 t0 the `:pper portion of fractionator 22 to serve as acooling and refluxing medium therein, while the remaining portion of thecondensate from receiver 29 may be withdrawn from the process throughline 31 and valve 38 to storage or elsewhere as desired.

The bottoms product in fractionator 22 will comprise principally 2,2,3,2,3,4, and 2,3,3-trimethylpentanes and may be withdrawn therefromthrough line 39`,and valve 40 to pump 4I by means of which it may besupplied to furnace 42 having heating coil 43 disposed therein. Inpassing through coil 43, the hydrocarbons are heated to the desiredtemperature which, as heretofore set forth, will be within the range of350 to '700 F. and preferably within the range of 400 to 650 F., at asuperatrnospheric pressure which will be correlated with the temperaturein order to obtain the desired demethylation. It has been found thatwhen higher pressures are employed, generally higher operatingtemperatures are required. In one specific operation of the presentprocess, the hydrocarbons are heated in coil -43 to a temperature ofabout 500 F. at a superatmospheric pressure of about 510 pounds persquare inch.

The heated products are withdrawn from coil 43 through line 44 and maybe supplied through valve 45 to mixing chamber 46. In chamber 46,hydrocarbons are admixed with separately heated hydrogen, the latterbeing introduced'to the process through line 41 containing valve 48 andsupplied to heating coil 49 disposed in furnace 50. The hydrogen isheated to the desired temperature and then supplied through line '5I andvalve 52 into mixing chamber 46. Mixing chamber 46 may comprise anysuitable apparatus and may or may not contain a bed of packing. Thefunction of the mixing chamber is to obtain intimate mixing of thehydrocarbons and hydrogen and also to separate out any unvaporizedmaterial. The unvaporized material may comprise, for example,lubricating oil fractions which are carried over with the hydrogen fromthe compressors. The unvaporzed material may be withdrawn from chamber4S through line 53 containing valve 54.

It is understood, when desired, that the hydrogen and hydrocarbons' maybe heated in admixture in one heating zone and that mixing chamber .46may be omitted. Even in case separate heaters are provided for thehydrocarbons and hydrogen, mixing chamber 46 may be omitted and theheated hydrocarbons may be directed from line 44 through line 55containing valve 56, while the heated hydrogen may be directed throughline 51 containing valve 58. The heated hydrogen and hydrocarbons maythen be directed, either through line 59 and valve 60 from mixingchamber 46 or through by-pass lines 55and 51, into reactor 6|, which maycomprise any suitable apparatus and which contains a suitablehydrogenating catalyst as heretofore set forth.

One of the important features of the demethylation process is that thetemperature within the reaction zone must be maintained within a criti-.cal narrow range. When the temperature in this zone becomes too high,there is excessive demethylation of the hydrocarbons and, on the otherhand, if the temperature is too low, selective demethylation does notoccur to any substantial extent. As heretofore set-forth, the exacttemperature will depend upon the pressure. One particularly suitablemethod of maintaining close control of the temperature is by means of areactor, as illustrated, containing tubes in which the catalyst isdisposed, and provision for circulating a heat exchange medium in theannular space surrounding the tubes. Reactor 6| is therefore preferablyof this form, although it is understood that other suitable types ofreaction zones may be employed.

' In order to maintain close control of the reaction temperature, drum62 may be filled with any suitable heat exchange medium, such asDowtherm, tetralin or the like, which circulates in a thermo-Siphonsystem through line 63,v line 64 and valve 65 into the space surroundingthe tubes in reactor 6| and is returned by way of line 66 to drum 62.The vaporous material from drum 92 passes through line 61, valve 68 andline 69 into and through condensery 10 containing suitable cooling meanssuch as closed coil 1|. The condensate from the'condenser passes throughrundown line 12 back'into drum 62. Drum 62 and accordingly the spacesurrounding the catalystcontaining tubes in reactor 6| will be operatedat the desired pressure in order to maintain the heat exchange medium inthe space surrounding the catalyst-containing tubes as a boilingliquid.'A

This may be any suitable superatmospheric pressure or, in certain cases,may even comprise subatmospheric pressure, depending upon the particularheat exchange medium employed. .Vacuum operation may be accomplished bymeans of vacuum .iet 13 havingline 14 and valve 15 for the introductionof steam or other suitable gas and outlet line 16, and being incommunication with condenser 10 by means oi line 69 and valve 11. Evenwhen superatmospheric pressure is employed in drum 62, vacuum jet 13 andits appurtenances may be employed at the start of operation orintermittently during operation, if desired, to remove incondensablegases from the system. These incondensable gases interfere with thepressure on the heat exchange medium and therefore must be vented asrequired.

The demethylation reaction is -highly exothermic and usually willliberate enough heat to maintain the heat exchange medium at the desiredtemperature. However, in case additional heat is required and also inorder to start up the unit, all or a portion of the heat exchange mediummay be directed from line 63 through is heated to the desiredtemperature, and the heated material may be directedvthrough line 82containing valve 83 into the surrounding space in reactor 6|. Anextension of line 63 containing valve 94 is provided either for theintroduction of heat exchange medium to, or the withdrawal of the heatexchange medium from the process.

Since the temperature of the demethylation reaction is so closelyrelated to the pressure, in another embodiment of the -invention atemperature differential of from about 10 to about 20 F. may bemaintained between the inlet and outlet sections of reactor 6|. As thehydrogen is consumed in the lower portion of the reaction zone, thereoccurs a decrease in available hydrogen and accordingly a. reduction inpressure in the upper portion of the reaction zone. One particularlysuitable means of accomplishing the temperature differential in reactor6| is by maintaining a pressure diierential between the upper and lowersections of the space surrounding the catalyst-containing tubes, sincethe temperature of the liquid therein is dependent upon the pressure.This difference in pressure may be obtained by maintaining a level ofliquid in drum 62, as illustrated diagrammaticaliy by line 85, andaccordingly in the surrounding space in reactor 6|, as indicated by linethe liquid levels being approximately the same height as the level ofcatalyst in the tubes of reactor 6|. The pressures at the lower portionof the surrounding space and drum will thereby be higher due to thefluid headrof the liquids therein.

Although upow. of hydrocarbons and hydrogen is illustrated in reactor6|, it is understood that downlow may be used. Thevproducts from reactorV6| may be withdrawn therefrom through line 86 containing valve 81 intoand through condenser 88, line 89 and valve 90, and may be supplied toflash zone 9|. Line 55' containing valve 56 is provided in order toby-pass the reactor and supply the heated hydrocarbons directly intoline 86. This by-pass will be used primarily in case excessivetemperatures develop in reactor 6|. A sumcient reduction in thetemperature in the reaction zone may be accomplished solely by means ofby-passing the reactor in this manner. When desired, hydrogen from line41 or line 96 may be supplied through valve 5|' and line 5| and theunheated hydrogen passed through lines 51 and 59 into reactor 6| inorder to effect all or a part of the desired cooling.

Flash zone 9| may comprise the first of a series of flash zones beingoperated at successively decreasing pressures, as illustrated by flashzones 9| and 92. It is understood, however, that one -or three or more,and preferably three, of such head fraction will be released which willbe high in hydrogen content. This overhead fraction may then be directedthrough line v93 and valve 94 to compressor, pump or the like 95, bymeans of which the hydrogen may be supplied through line 96 and valve 91into line 41'for treatment in the manner as heretofore set forth. Y

The unvaporized bottoms from flash zone 9| which will containsubstantial proportions of methane, may be withdrawn therefrom throughline 98 and reduced in pressure as it passes through valve 99 andintroduced into flash zone 92. Assuming that three flash zones areemployed, the pressure reduction may be from about 200 pounds in thefirstnash zone to about 70 pounds in the second flash zone and down toabout 25 pounds in the third flash zone. It is understood that thepresent invention is not limited to these particular pressures and anysuitable series of pressure reductons may be employed. A level ofunvaporized liquid is likewise preferably maintained in flash zone 92but, in this case, the liberated overhead fraction will be rich inmethane and may be withdrawn from Zone 92 through line and valve |0| andthen may be passed through line |02, wherefrom a portion may be removedfrom the process through line |03 but, in accordance with the preferredembodiment of the present invention, at least a portion thereof isdirected through line |04 and valve '|05 for further treatment in themanner to be hereinafter described in detail. In case only oneflash zoneis employed or for other reasons, all or a portion of the overheadfraction from flash zone 9| may be directed through line |02 and valve|05 for removal from the process or treatment in the manner to behereinafter described in detail.

Any other suitable means of separating a methane fraction may also beemployed within the scope of the present invention and this maycomprise, for example:

(1) Absorblng the methane .in a liquid stream and subsequently strippingthe methane therefrom.

(2) Absorbing the methane on a suitable solid adsorbent, such asactivated carbon or the like, and then subsequently stripping themethane therefrom.

It is understood, however, that these various alternative means are notnecessarily equivalent in their efficiency in separating the methanefrom tbe other products. The unvaporized material in ash zone 92 may bewithdrawn from the lower portion thereof through line |01 and valve |08to pump |09, by means of which it may be directed through line ||0 andvalve into fractionator I2. Fractionator ||2 may be similar to theheretofore described fractionators, having reboiler I3 or other suitableheating means in the lower portion thereof, and will function toseparate an overhead fraction having an end boiling point of about 158F. from higher boiling material. The overhead fraction, which willcomprise principally pentane, 2,2 and 2,3-dimethylbutane, may bewithdrawn froml the upper portion of fractionator ||2 through line ||4,valve ||5, condenser IIB, rundown line `and valve ||8 into receiver ||9,having conventional gas release line |2| containing valve |20. Thecondensate in receiver ||9 may be withdrawn therefrom through line |22and valve |23 to pump |24, by means of which a regulated portion thereofmay be recycled by Way n( line |25 and valve |26 to the upper portion offractionator ||2 to serve as a cooling and refluxing medium therein,while the remaining portion of the condensate from receiver ||9 may bewithdrawn from the process by way of line |21 andv valve |28 to storageor elsewhere as desired.

The bottoms product may be withdrawn from fractionator ll2'through line|29 and valve |30 te pump |3| by means of which it may be directedthrough line |32 and valve |33 to fractionator |34, which may be similarto the heretofore described drawn from the lower portion of fractionator|34 through line |36 and may be withdrawn from the process through line|31 but, in a preferred embodiment of the invention, at least a portionof this stream is directed through line |33 and valve |39 to pump |40 bymeans of which it is directed through line |4| and valve |42 into line20 to be supplied into fractionator 22 for separation and furthertreatment within the process in the manner heretofore set forth. Thus,the 2,3-dirnethylpentane will be recovered in the overhead fraction fromfractionator 22, while the trimethylpentanes will be supplied in thebottoms fraction to demethylation treatment.

.The overhead fraction from lfractionator |34, which will compriseprincipally triptane, may be withdrawn therefrom through line |43, valve|44, condenser |45, rundown line |46 and valve |41 to receiver 48,having conventional gas release line |49 containing valve |50. Thecondensate from receiver |48 may be withdrawn therefrom through line |5|and valve |52 to pump |53, by means of which a regulated portion thereofmay be recycled by way of line |54 containing valve |55 to the upperportion of fractionator |34 to serve as a cooling and refluxing mediumtherein, while theremaining-portion of the triptane product may bewithdrawn through line |56 and valve |51 and recovered as a finalproduct of the process.

In accordance with a preferred embodiment of the present invention, themethane fraction being supplied through line |04 may be subjected tosuitable treatment for conversion thereof into hydrogen. vOne suitableprocess comprises the so-called water-gas reaction in which the methanefraction is treated with water in the form of steam at elevatedtemperatures in the presence of suitable catalysts to form hydrogen.This Aprocess is well known and no novelty is claimed the particularcatalyst and other conditions of4 operation and in some cases it may beas low as 600 F. while in other cases may be as high as 1800 F. It isunderstood that the present invention is not limited to any particularcatalyst or temperature employed in this step of the process since theonly requirement, insofar as the combination aspect of the presentinvention is concerned, is that at least a portion of the methane beconverted into hydrogen. In this process, carbon dioxide and some carbonmonoxide is usually produced and it is preferred to utilize a suitablesolvent or other means for separating the carbon oxides from thehydrogen in order to leave a substantially pure hydrogen product.

Another method of converting the methane into hydrogen within the scopeof the present invention is by cracking the methane either in thepresence or absence of suitable catalysts. In this method of operationthe temperature employed is usually within the range of from about 1200to about 1800 F. When employed, any suitable catalyst may be used andhere again a large variety of catalysts have been proposed for effectingthe decomposition of methane into hydrogen.

-Referring again to the drawing, the methane fraction being suppliedthrough line |04 may be directed into heating coil |58 disposedinfurnace |59. In case the water-gas reaction is employed,

steam may be introduced through line |60 and valve 6| to commingle withthe methane fraction in line |04 and then directed into heating coil|58. If the methane conversion step comprises the cracking of themethane, line |50 may be omitted or it may be utilized for theintroduction of addi- .tional methane from an extraneous source or forany other desired purpose. The heated products from coil |58 may bedirected through line |62 and valve |63 into reactor |64. The catalyst,when employed, may be disposed within reactor |64 and the heatedhydrocarbons suitably contacted therein. Either up or downflow may beemployed, as desired. The exact form of reactor |64 will depend upon theparticular process being employed. The products from reactor |64 may bedirected through line |65 and valve |66 to separator and purifier |61.'I'he design of zone |61 will depend upon the particular processutilized for converting the methane into hydrogen. For example, in casethis process comprises the water-gas reaction, zone I 61 preferablyconsists of one or more. fractionating zones in which the products aretreated with a suitable solvent or other means in,

products. Unconverted methane may be withdrawn from the lower portion ofzone |61 through line |68 and may be removed from the process throughvalve |68 or all or a portion thereof may be recycled by way of line|10, valve |1| and line |04' to heating coil |58 for further conversiontherein.

The hydrogen separated in zone |61 may be withdrawn therefrom throughline |12 and may be directed through line |12' and valve |13 into line41 to be supplied to the demethylation step of the process in the mannerheretofore set forth. Usually the hydrogen recovered from zone |61 willbe saturated with moisture at the temperature conditions at which it isrecovered. As heretofore stated, moisture is detrimental to thedemethylation catalyst and, in the preferred embodiment of the presentinvention, the hydrogen fraction is directed from line |12 through line|14 and valve |15 into dryer |16. It is also within the preferredembodiment of the invention that, when the hydrogen introduced to theprocess from an extraneous source contains moisture, the hydrogen beintroduced to the process through line |11 and valve |18, instead ofthrough line 41 and valve 48 as heretofore set forth. Dryer |16 maycomprise any suitable apparatus and contain any suitable absorbentmaterial, such as alumina or the like, in order to reduce the watercontent of the hydrogen fraction to as low as practicably possible andpreferably to completely remove thewater. Either upiiow or downilow maybe employed in dryer 16, as desired, and the dried hydrogen fraction maythen be directed through line` |18 and valve |80 into lines |12, |12'and 41 to be supplied to the demethylation step of the process asheretofore set forth.

It is a particular feature of the combination aspects of the presentinvention that at least sufficient hydrogen will be produced in themethane conversion step of the process to meet the requirements of thedemethylation reaction. When the methane conversion step comprises avorder to separate the hydrogen Afrom other io water-gas reaction, threemolecules of hydrogen are theoretically obtainable from one molecule ofmethane and one molecule of steam, or four molecules of hydrogen aretheoretically obtainable from one molecule of methane` and two moleculesof steam, depending upon whether carbon monoxide or carbon dioxide isformed. Likewise, in the cracking of methane, two molecules of hydrogenare theoretically possible from one molecule of methane. Since themethane conversion step will convert at least 50% and usually a muchhigher proportion of the methane into hydrogen, it is readily seen thatsuilcient hydrogen to meet vthe requirements of the demethylationprocess will be available, thus providing a unitary process. Any excesshydrogen may be withdrawn from the system through an extension of line|12 and valve |13'.

'I'he following example is introduced to further illustrate the noveltyand utility of the present invention but not with the intention of undullimiting the same.

The charging stock to the process may comprise 65.4 moles per day(equivalent to 1257 gallons per day) of an isooctane fraction asheretofore described and is supplied at a temperature of F. tofractionator 3 whichmay be operated with a top temperature of 215 F. anda bottom temperature of 245 F. A bottoms fraction comprising 13 molesper day (equivalent to '251 gallons per day) of higher boiling bottomsis withdrawn and recovered, while an overhead fraction comprising 52.4moles per day (equivalent to 1006 gallons per day) issupplied tofractionator 22 which may be operated with a top temperature of 211 F.and a bottom temperature of 230 F. An overhead fraction comprising 34.7moles per day (equivalent to 662 gallons per day) and comprisingprincipally 2,2,4-trimethylpentane is recovered from fractionator 22.The bottoms product from fractionator 22 comprises 30.4 moles per day(equivalent to 573 gallons per day). A hydrogen fraction containing 91.2moles per day of hydrogen and 9.1'moles per day of methane, to make atotal of 100.3 moles per day of gas, is heated to a temperature of about500 F. at a pressure of about 500 pounds per square inch. 'Ihe bottomsfraction from fractionator 22 is likewise heated to a temperature of 500F. at a pressure of about 500 pounds and the heated products aresupplied to reactor 6| containing a hydrogenating catalyst comprising 66per cent by weight of total nickel, 30 per cent of diatomaceous earthand 4 per cent of oxygen as nickel oxide.

Reactor 6| may comprise an insulated reaction i chamber having catalystscontaining tubes disposed therein and communicating with drum 62containing Dowtherm. 'I'he Dowtherm is maintained at a pressure of 12pounds absolute at the top and 14 pounds absolute at the bottom, and

the circulation rate is controlled so that the temperature of the heat.exchange medium in the lower portion of the space surrounding the tubesin reactor 6| is about 490 F. and the temperature in the upper portionof this space is about 480 F.

'I'he demethylation products are Withdrawn from reactor 6| at atemperature of about 495 F., cooled in condenser 88 to a temperature of90 F., and then supplied to flash zone 9| at a, pressure of about 200pounds per square inch. A fraction rich in hydrogen is withdrawn fromthe upper portion of zone 8| and is recycled to the demethylationprocess, while the liquid products are flashed in a second flash zone ata pressure 11 of about 70 pounds and then flashed in a third flash zoneat a pressure of about 25 pounds per square inch. The overhead productsfrom the second and third ash zones are supplied to treatment in themethane conversion step of the process.

The bottoms product from the last flash zone is supplied to fractionator|I2 which may be operated with a top temperature of 130 F. and a bottomtemperature of 185 F. An overhead product comprising principally 2,2-and 2,3-dimethylbutane is separated and recovered as one of the naiproducts of the process. The bottoms product from fractionator I l2 issupplied to fractionator |34 which may be operated with a toptemperature of 185 F. and a bottom temperature of 200 F. An overheadfraction comprising triptane is separated and recovered as a ilnalproduct of the process, while the bottoms product from fractionator |34may be recycled to fractionator 22 for further separation and treatmentwithin the process.

In a process such as h'ereinbefore described, there may be produced,based upon an isoqctane fraction charge of 1257 gallons per day, thefollowing products:

Gallons per day Higher boiling isooctane bottoms 2512,2,4-trimethylpentane and 2,3-dimethylpeni-,ane frartinn y 2 80 2,2 and2,3-dimethylbutane fraction 77 Triptane fraction 193 The triptanefraction will be of high purity and will be particularly suitable forblending in aviation gasoline or may be used for any other desiredpurpose.

The previously separated methane fractions are reacted with steam in thepresence of a nickelcatalyst promoted with alumina at a temperature ofabout 1300 F. to produce carbon monoxide and hydrogen. The products maythen be reacted with additional steam at about 900 F. in the presence ofan iron oxide catalyst promoted with chromium oxide to form carbon`dioxide and hydrogen. The carbon dioxide may be separated from thehydrogen by absorption in a solvent comprising ethanol amine, and thehydrogen may then be supplied to the demethylation process in the mannerhereinbefore described.

We claim as our invention:

1. A process for the production of triptane from anisooctanefractioneomprisingl 2,2,4-,2,2,3-,2,3,4- and 2,3,3-trimethylpentanes andhigher boiling compounds, which comprises ractionating said isooctanefraction to separate higherv boiling compounds from thetrimethylpentanes, further fractionating the trimethylpentanes toseparate 2,2,4- trimethylpentane from a fraction comprising the othertrimethylpentanes, heating the last mentioned fraction to a selectivedemethylation temperature, simultaneously heating a hydrogen fraction tosubstantially the same temperature, commingling the heated fractions andcontacting the same with a nickel catalyst at a temperature of theorderof 500 F. and at a. superatmospheric pressure of the order of 500pounds per square inch, hashing and reducing the pressure of theproducts of said demethylation to a pressure of the order of 200 poundsper square inch to separate a hydrogen fraction, recycling the hydrogenfraction to said demethylation, further reducing the pressure of saidproducts to apresvsure of the order of v pounds per square inch toseparate a methane fraction, fractionating the remaining products toseparate an overhead fraction containing 2,2- and 2,3-dimethylbutanesfrom higher boiling products, further fractionating the higher boilingproducts to separate a triptane fraction from higher boilingtrimethylpentanes.

2. The process of claim 1 further characterized in that at least aportion of the last mentioned higher boiling trimethylpentanes isrecycled to further selective demethylation treatment.

3. The process of claim 1 further characterized in that the amount ofhydrogen is of the order of 3 moles of h'ydrogen per mole of said othertrimethylpentanes.

VLADIMIR HAENSEL. VLADIMIR N. IPATIEFF.

REFERENCES CITED The following references are of record in the 4ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,004,632 Day Oct. 3, 19111,365,849 Ramage Jan. 18, 1921 1,878,580 Gray Sept. 20, 1932 2,209,346 yMcCausland July 30, 1940 2,270,303 Ipatiei Jan. 20, 1942 2,181,690Deanesly et al. Nov. 28, 1939 2,184,930 Ruys et al Dec. 26, 19392,214,463 Ipatieff et al Sept. 10, 1940 OTHER REFERENCES Nat. Pat. News,June 15, 1938, R-291, IRP-292, Rf-294, and R-296. (Pat. Oi. Lib.)

